The present invention relates to a low fat peanut butter like product and, more particularly, to a low fat peanut butter product which is shelf stable at room temperature without pasteurization, addition of antimicrobial agents and/or heat treatment during preparation.
Peanut butter is a highly nutritious food containing a high level of protein. However, peanut butter also contains relatively large quantities of fat. A typical peanut butter product has an oil content of approximately 50%. Due to the high oil content and its inherently low moisture level, the typical peanut butter is highly stable at room temperature, without refrigeration, for a substantial period of time. Stable or shelf-stable in this context refers to the relative inhibition of the propagation of mold, fungus and/or bacteria.
To be labeled as peanut butter invokes various regulations of the United States Food and Drug Administration (FDA), among which: the peanut ingredients must comprise of at least 90% of the weight of the finished product. As a result, conventional peanut butter has a high oil content, with little or no appeal to health conscious consumers.
There has been a substantial amount of research directed toward reducing the caloric content of peanut butter. A thirty two gram serving of conventional peanut butter typically contains 200 calories, of which 70% are derived from a corresponding fat content of 16 grams per serving. A low-calorie, low-fat diet is imperative for many consumers with health concerns.
Most of the methods heretofore employed for oil/fat reduction use partially defatted peanut flour in conjunction with full or reduced fat peanut paste. Water may be added in varying amounts which, in turn, provides for higher moisture levels in the finished product. The term "water activity level" is described by Norman N. Potter in the book "Food Science", Third Edition, A.V.I. (1984) as a qualitative measure of unbound free water in a system that is available to support biological and chemical reactions. In general, as the water activity of a given food product decreases, its shelf life increases. A high water activity (Aw) product becomes more susceptible to mold, fungus and bacterial proliferation. For instance, the FDA defines a low acid food product with a pH of greater than 4.6 as shelf stable only if it has a water activity of 0.85 or less. Two foods with the same water content can vary significantly in their water activity depending on how much free water is in the system. When a food is in moisture equilibrium with its environment, the water activity of the food will be quantitatively equal to the relative humidity in head space of the container divided by 100.
Invariably, a high moisture content raises shelf life concerns. As a result, heat treatment of conventional peanut butter is essential. However, it has been determined that heating a low fat peanut butter with high moisture content will produce off flavors in addition to adversely impacting the color of the finished peanut butter. Carmalization and browning reaction takes place during the heat treatment which impart an undesirable appearance to the product. Alternatively, antimicrobial agents may be added, but only at the risk of limiting appeal to health conscious consumers. In any event, refrigeration of such a high moisture content product is essential in order retard the growth of mold, fungus, bacteria and the resulting spoilage. For example, the products described in US Patent No. 4,828,868 have a water activity over 0.95 and would be expected to require continuous refrigeration before and after opening.
The prior art is instructive by way of how the foregoing concerns have been approached. For instance, Yokoyama, et al., U.S. Pat. No. 4,814,195, teaches a reduced calorie peanut butter product containing from about 15 to about 40% by weight of a solid bulking agent having from 0 to about 3 calories per gram. However, the described products use polydextrose and microcrystalline cellulose, both of which require special pre-processing.
U.S. Pat. No. 4,828,868 to Lasden, et al. is directed to a low calorie, low fat peanut butter like product and the method for making the product. The method entails using unroasted defatted or partially defatted peanut flour having no more than about 35% fat by weight which is milled in the presence of water to a maximum particle size of about 150 microns. The water and flour mixture is then cooked at a temperature between 175.degree. F. and the boiling point of the mixture. The moisture level of the finished product is high and would invariably necessitate that product be refrigerated for extended shelf life.
As another approach, U.S. Pat. No. 5,240,734 discloses a reduced fat peanut butter which is prepared as a water in oil emulsion containing a continuous peanut butter oil phase, a protein complexing agent, to maintain consistency of the oil phase, and a discontinuous aqueous coagulated protein phase, to reduce the fat content of the peanut butter. The discontinuous phase contains a coagulable dairy or vegetable protein and a protein coagulating agent.
A further example of an attempt to produce a low fat peanut butter is U.S. Pat. No. 5,302,409, in which a reduced fat peanut butter is made by removing oil from ground peanuts, preferably removed by centrifuging the ground peanuts until a supernatant oil layer is formed then decanted. The resulting peanut paste is then reground. Maltodextrin and modified food starch then can be added along with salt, butter flavoring, or peanut flavoring. This process is semicontinuous, thus limiting production. The product uses hydrated modified food starch which increases the moisture content and imparts a questionable shelf life.
U.S. Pat. No. 5,603,979 discloses a low fat peanut butter like product, shelf stable at room temperature. The product includes defatted peanut flour, water, humectant, soluble salt and a natural gum. The peanut butter product has a water activity of 0.80-0.85 and contains 70-95% less fat than conventional peanut butter. A pre-mix of hydrated natural gums is processed at elevated temperatures then mixed with conventional peanut butter. The mixed product has a high water content (approximately 24%) which must be heated/pasteurized at 180-190.degree. F. for about 1-10 minutes. The result is excessive browning and off-flavors which limit the palatability of the finished product.
U.S. Pat. No. 5,591,477 describes a method of producing reduced fat peanut butter without non-peanut supplements. The invention involves making peanut flour using a defatting process and then mixing the flour with ground roasted peanuts and a selected amount of peanut oil to produce a peanut paste. The method further involves adding sweetener, dextrin, salt, flavorants and/or fiber, blending the resultant into a peanut product, then remilling the peanut product. However, this product does not meet the definition of low fat because only 30% of the fat content is reduced.
U.S. Pat. No. 5,536,524 discloses a method for providing a reduced fat and reduced calorie peanut buffer composition by incorporating therein an indigestible synthetic fat substitute, a polyol fatty acid polyester having at least four esterified hydroxyl groups. The polyol polyester is present in the mixture at a level from 10-25% by weight, resulting in a total fat content of 45-55% by weight, such that the final product has a reduced level of digestible fat. The acceptability of such a product is questionable due to the well-documented public resistance to incorporation of synthetic fats in food products and concerns over adverse physiological effects.
U.S. Pat. No. 5,230,919 discloses a reduced fat peanut butter produced using partially defatted peanut solids combined with regular peanuts under high shear mixing conditions. The defatting process is semi-continuous and comparatively expensive. The milling parameters are crucial. The process requires substantial reintroduction of peanut oil to produce a flowable product. The result is a rather exacting process which necessitates a high product cost.
U.S. Pat. No. 5,366,754 discloses a method for preparing a low fat, high moisture peanut butter composition and characterized by the following: 0-50% peanut flour, less than about 1% peanut oil, a peanut source from either a peanut paste derived from non defatted peanuts having about 50% peanut oil or a partially defatted peanut paste containing approximately 12-30% peanut oil. A humectant and emulsifier system is present at a level sufficient to provide a water activity of less than 0.91, but not so low as to dispense with antimicrobial agents and/or pasteurization, which are still required to extend the shelf life.